Plants and soil microbes respond to recent warming on the Antarctic Peninsula

Increases in temperature on the Antarctic Peninsula during the latter part of the 20th century were accompanied by an acceleration in moss growth, scientists have learned. Writing in the journal Current Biology they describe the activity as unprecedented in the last 150 years.

The Peninsula sustains moss banks some of which are more than 5000 years old. A team from British Antarctic Survey (BAS), the University of Cambridge and the University of Exeter sampled the most southerly known moss bank, at Lazarev Bay on Alexander Island, in 2008. The researchers extracted a short peat core from the bank and, using radiocarbon dating techniques, ascertained the start of peat accumulation to have been around the year 1860. Microscopic tests established it was formed from a single species (Polytrichum strictum).

The Antarctic Peninsula is known to have witnessed significant warming since the 1950s, when official records started. Records from BAS’ Rothera research station show the Peninsula warmed by between 1 and 1.4°C per decade during the 1980s and ‘90s. Along with one of the fastest rates of warming anywhere on the planet, the Peninsula has also seen significant increases in precipitation. The length of the melt season has been steadily increasing since 1948 with earlier thawing and later freezing extending the growing season.

These trends have led to changes in the physical environment of the Peninsula. Ice cover has reduced, exposing land to settlement by a variety of flora, the most common of which is moss.

The sampled moss bank accumulated at around 1.25 mm a year throughout the late 19th and early 20th centuries then increased its growth rate from the mid-1950s to reach 5 mm a year by the late 1970s. It is now estimated to be 3.5 mm a year.

Lead author, Jessica Royles, from BAS and the University of Cambridge, said: "This moss bank provided a unique archive of growing conditions on the Antarctic Peninsula over the past one hundred and fifty years. By combining multiple analyses we have clearly demonstrated a substantial increase in plant growth since the 1960s, coincident with changes to the local climate."

Microscopic analyses of the peat samples revealed that one species of testate amoebae (Corythion dubium) was highly dominant. The testate amoebae probably colonised the moss bank soon after it was established. There was a big expansion in its population between the 1960s and 1990s followed by a slight decline in the early part of the 21st century.

Co-author, Matthew Amesbury, of the University of Exeter, said: "The presence of testate amoebae in very low numbers from the base of the core showed that these tiny creatures colonised the moss bank early, despite extremely cold and dry conditions. However, the rapid increase in temperature since the 1950s has allowed the amoebae to increase their numbers dramatically, indicating that the ecology of the soil-plant system has fundamentally changed."

The biological records in this region stretch back further than the meteorological records do, so this latest research will help scientists’ improve their understanding of the interaction between diversity and climate.